1. Field of the Invention
The present invention relates to a temperature detecting circuit and, more particularly, to a temperature detecting circuit that can be exactly implemented since trimming is possible depending on variation in process or voltage and that can significantly reduce consumption of the standby current since the refresh period is differentiated depending on temperature, in such a manner that the width of variation in temperature that can be detected by the temperature detecting circuit can be widened using a plurality of detectors, the status of the plurality of the detectors can be detected at the outside by an encoder, and one of the detectors that can detect correct temperature information by transferring fuse trimming information from the outside to the detecting means via the select means.
2. Discussion of Related Art
In semiconductor devices, if a device requiring a periodical refresh so as to keep data is needed, a large amount of standby current is necessary for a self-refresh. The refresh period that is actually required, however, very differs depending on temperature. If temperature is detected and the refresh period is varied depending on temperature, the standby current can be significantly reduced. The exactness of a common temperature detecting circuit, however, is lowered depending on variation in external conditions such as process, voltage, and the like.
FIG. 1 is a block diagram illustrating the construction of a conventional temperature detecting circuit.
A first delay means 11 receives an input signal (IN) as an input to output a reference signal (ref) depending on temperature that will be detected without being influenced by variation in operating environments such as change in process, voltage, temperature, etc. A second delay means 12 outputs a delay signal (tem) whose delay value is changed depending on variation in temperature. A detector 13 receives the reference signal (ref) from the first delay means 11 and the delay signal (tem) from the second delay means 12, as an input and then outputs (dout) a detecting signal (det) indicating whether the delay signal (tem) is lower or higher the reference signal (ref) to the outside through a DQ buffer 14.
As such, the detection width of temperature is controlled by correcting the delay width of the first delay means 11 or the second delay means 12 using the data outputted via the DQ buffer 14.
In the conventional temperature detecting circuit constructed above, however, since only one detector is employed, the width of variation in temperature that can be detected depending on variation in process or voltage is limited. Therefore, if the width of variation in temperature that can be actually detected by a device is large, the device fails to serve as the temperature detecting circuit.